1. Field of the Invention
The present invention relates to a fluorescent lamp and a luminaire.
2. Description of the Prior Art
Recently, a tricolor fluorescent lamp having a phosphor layer comprising phosphors emitting blue, green and red is widely used for main illumination in houses and stores.
In this tricolor fluorescent lamp, highly efficient rare earth activated phosphors are commonly used. Examples of commonly used phosphors include a bivalent europium activated barium magnesium aluminate blue phosphor, a bivalent europium activated strontium chlorophosphate blue phosphor, a trivalent cerium and trivalent terbium activated lanthanum orthophosphate green phosphor, a trivalent europium activated yttrium oxide red phosphor or the like. The tricolor fluorescent lamp has a higher luminous flux and a higher color rendering than a fluorescent lamp using a calcium halophosphate phosphor Ca10(PO4)6FCl: Sb, Mn, which emits white alone, as a phosphor layer, so that it is widely used in spite of its expensiveness.
The tricolor fluorescent lamp can create different light colors by changing the ratio of blending of blue, green and red phosphors used in the lamp. Fluorescent lamps for general illumination purposes can be classified roughly into lamps in a low color temperature region of not more than 3700 K, lamps in a medium color temperature region ranging from 3900 to 5400 K, and lamps in a high color temperature region of not less than 5700 K.
The correlated color temperature of the fluorescent lamp affects the atmosphere of an illuminated space to a large extent. For example, it is known that a lamp in a low color temperature region creates a relaxed and warm atmosphere, and a lamp in a high color temperature region creates a cool atmosphere.
Colors reproduced by a variety of light sources usually are quantified and compared based on the color rendering index (generally, general color rendering index). The color rendering index evaluates quantitatively how faithfully an illumination light reproduces colors, compared with a reference light. As the reference light, a blackbody radiation or CIE daylight illuminant having the same correlated color temperature as that of the illumination light is used.
At the present, the fluorescent lamps having a correlated color temperature of not less than 3900 K predominantly are used in houses and stores. However, recently, fluorescent lamps in a low color temperature region with a correlated color temperature of 3700 K or less are used increasingly, although gradually, in order to create a relaxed atmosphere in an illuminated space.
However, the light color of the lamp in a low color temperature region with a correlated color temperature of 3700 K or less is highly yellowish, and the color of an illuminated object is not so colorful, so that the object overall looks dull, even though the lamp is a tricolor fluorescent lamp having a high color rendering index. Thus, the color of the illuminated object looks less agreeable under illumination with a fluorescent lamp in a low temperature region, although the fluorescent lamp has an equal general color rendering index.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a fluorescent lamp and a luminaire that can radiate illumination light having a correlated color temperature of 3700 K or less that allows the color of an illuminated object to look agreeable, even though the light color is in a low color temperature region, by making the color of the illuminated object more colorful.
In order to achieve the object, a fluorescent lamp of the present invention includes a phosphor layer containing a blue phosphor having an emission peak in the 440 to 470 nm wavelength range, a green phosphor having an emission peak in the 505 to 530 nm wavelength range, a green phosphor having an emission peak in the 540 to 570 nm wavelength range, and a red phosphor having an emission peak in the 600 to 670 nm wavelength range. The ratio I1/I2 of the emission peak energy I1 in the wavelength range of 506 to 530 nm to the emission peak energy I2 in the wavelength range of 540 to 570 nm is not less than 0.06, and the correlated color temperature of the lamp is not more than 3700 K.
This embodiment provides a fluorescent lamp in a low color temperature region in which the colorfulness of a color of an object perceived under illumination is improved.
In the fluorescent lamp, it is preferable that the ratio I1/I2 of the emission peak energy I1, in the wavelength range of 505 to 530 nm to the emission peak energy I2 in the wavelength range of 540 to 570 nm is in the range from 0.06 to 0.50. This preferable embodiment provides a fluorescent lamp in a low color temperature region in which the colorfulness of a color of an object perceived under illumination is improved and the color looks agreeable.
In the fluorescent lamp, it is preferable that the color point of the lamp is present in a region where the sign of the chromaticity deviation from the Planckian locus is minus in the CIE 1960 UCS diagram. This preferable embodiment provides a fluorescent lamp in a low color temperature region in which the colorfulness of a color of an object perceived under illumination is improved further.
In the fluorescent lamp, it is preferable that the color point of the lamp is present in a region where the chromaticity deviation from the Planckian locus is in the range from xe2x88x920.007 to xe2x88x920.003 in the CIE 1960 UCS diagram. This preferable embodiment provides a fluorescent lamp in a low color temperature region in which the colorfulness of a color of an object perceived under illumination is improved further and the color looks agreeable.
In the fluorescent lamp, it is preferable that the blue phosphor having an emission peak in the 440 to 470 nm wavelength range is a blue phosphor that is activated with bivalent europium.
In the fluorescent lamp, it is preferable that the green phosphor having an emission peak in the 505 to 530 nm wavelength range is a green phosphor that is activated with bivalent manganese.
In the fluorescent lamp, it is preferable that the green phosphor having an emission peak in the 540 to 570 nm wavelength range is a green phosphor that is activated with trivalent terbium.
In the fluorescent lamp, it is preferable that the red phosphor having an emission peak in the 600 to 670 nm wavelength range is a red phosphor that is activated with at least one selected from the group consisting of trivalent europium, bivalent manganese and tetravalent manganese.
In order to achieve the object, a luminaire of the present invention radiates illumination light including a combination of emission lights whose emission peaks in the 440 to 470 nm, 505 to 530 nm, 540 to 570 nm, and 600 to 670 nm wavelength ranges. The ratio I1/I2 of the emission peak energy I1, in the wavelength range of 505 to 530 nm to the emission peak energy I2 in the wavelength range of 540 to 570 nm is not less than 0.06, and the correlated color temperature of the illumination light is not more than 3700 K.
This embodiment provides a luminaire radiating illumination light in a low color temperature region in which the colorfulness of a color of an object perceived under illumination is improved.
The luminaire preferably includes a light source and at least one selected from the group consisting of a transmitting plate and a reflecting plate for converting light radiated from the light source to the illumination light.
In the luminaire, it is preferable that the ratio I1/I2 of the emission peak energy I1, in the wavelength range of 505 to 530 nm to the emission peak energy I2 in the wavelength range of 540 to 570 nm is in a range from 0.06 to 0.50. This preferable embodiment provides a luminaire radiating illumination light in a low color temperature region in which the colorfulness of a color of an object perceived under illumination is improved and the color looks agreeable.
In the luminaire, it is preferable that the color point of the illumination light is present in a region where the sign of the chromaticity deviation from the Planckian locus is minus in the CIE 1960 UCS diagram. This preferable embodiment provides a luminaire radiating illumination light in a low color temperature region in which the colorfulness of a color of an object perceived under illumination is improved further.
In the luminaire, it is preferable that the color point of the illumination light is present in a region where the chromaticity deviation from the Planckian locus is in a range from xe2x88x920.007 to xe2x88x920.003 in the CIE 1960 UCS diagram. This preferable embodiment provides a luminaire radiating illumination light in a low color temperature region in which the colorfulness of a color of an object perceived under illumination is improved further and the color looks agreeable.
Thus, the present invention provides a fluorescent lamp and a luminaire that radiate illumination light having a correlated color temperature of 3700 K or less that allows colors of illuminated objects to look more agreeable by improving the colorfulness of the colors perceived under illumination.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.